Method of making bimetallic plates.



P. R. MoBERTY.

METHOD OF MAKING BIMETALLIG PLATES. APPLICATION TILED P113121, 1908.

I 1,046,824. Patented Dec. 10, 1912.

"if" g i f 6i a -i Iniventor:

NITE STATES ATENT orron.

FRANK R. MQBERTY, OF NEW ROCHELLE, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

umrHoD or MAKING BIMETALLIC P ATES.

' s eaaam of Letters Patent.

Patented Dec. 10, 1912.

To all whom it may con'cem:

Be it known that I, FRANK R. MCBERTY, a citizen of the United States, residin in the town of New Rochelle, county of. estchester, and State of New York, have invented a certain new and-useful Improvement in Methods of Making Bimetallic Plates, of which the following is a full, clear, concise, and exact description.

This invention is a method or process of making metallic plates or material.

The particular object in view is the provision of plates from which may be made a cheap and equally eflicient substitute for the considerable masses of platinum heretofore employed for contact pieces in electrical switches, such as telephone switches, relays and switch keys. 7

The material consists of' a facing of platinum, or other suitable metal having like characteristics, and a backing of a base metal. From this material suitable contact pieces may be formed to be secured in the contact parts in such a way as to leave the platinum face exposed but securely held, and so backed and supported that in the event of wearing through theplatinum, the efficiency of the contact shall not be at once seriously impaired.

The present invention provides a method for producing plates .ormaterial from which may be made contact pieces of moderate cost capable of fulfilling all the conditions described. -Each of these contact pieces is composed of a surface film of platinum foil, backed by a heavy plate of pure copper electrolytically deposited upon the.

platinum. Theplatinum foil may be one thousandth inch thick, while the copper backing may be one fiftieth inch thick.-

This material is produced in sheets, and from these, stampings are made in the form of cup shaped disks which are placed in recesses or perforations in the switch levers or elements, and crushed or flattened into the recesses to be securely held with the platinum face exposed in proper form. As this process of mounting the contacts produces a considerable distortion ofthe base metal and also of the same with relation to the platinum face, special means and processes must toe-employed for insuring adhesion between the platinum face and the backing,

and suitable malleability in the backing metal. I

The invention is illustrated in the accompanylng drawing.

In this drawing Figure 1 represents a m mandrel for holding the platinum foil during the process of plating. Fig. 2 represents the appliances for rotating the mandrel. bearing the platinum foil and for supplying to it at the same time a graduated current to produce the deposit. Fig. 3 represents the sheet of material.

As shown in Figs. 1 and'2, a cylindrical mandrel a is mounted vertically in an electrical plating bath, being made one pole of the plating circuit. This mandrel a is provided with clamps a by which a sheet of platinum foil 6, shown partly in section, may be folded about and secured to its cylindrical surface. The bottom of the mandrel may be covered with "wax or insulating material. The mandrel is mounted v upon the. end of a shaft 0, carried in a journal 0, and driven from a suitable motor 0 The mandrel depends in the electrolyte a? in the plating tank e, which contains also the tubular anode f, for its other pole. The cathode mandrel a with its covering Z) and the plate f, constitute the terminals of a circuit including a generator or battery f, and a regulating switch -For the purpose of producing a proper plating upon the foil b,the usual copper plating bath may be employed. The mandrel may have an approximate peripheral speed of 50 to 100 feet per minute. deposit the platinum foil is first washed with water, then with strong potash, with dilute nitric acid, and finally with distilled water, to produce a chemically clear surface. The mandrel is then inserted into the bath and set in rotation, 'after which the depositing current is applied, being raised gradually from an extremely low value to such a value per square inch as' begins to produce granules. The current should be connected at this low value for a short time-say 10 minutes, until a thin but continuous and coherent deposit appears ,upon the platinum plate, after which it may be raised rather rapidly.

The result of applying the current for a considerable time at a very low value is to produce an initial coating of copper which adheres very strongly to the cleaned surface of the platinum ;;thereby the composite contact is enabled to withstand the deformation.

In producing the during the mounting process without impairment of cohesion between the face and backing. The rotary process of plating produces an extremely fine grained, tough and malleable coating of pure copper. After a plating about one fiftieth of an inch thick has been produced, which may be mom or two hours, the mandrel is removed and the platinum foil I), backed with a layer of copper, is stripped ofl, the plate being bent out flat as illustrated in Fig. 3.

I claim: I

1. The herein described method of producing bimetallic plates or material which consists in covering one side'of a sheet of platinum foil, cleaning the other side, and

electro-plating thereon an. adherent coating of copper by beginning the plating with a feeble current, and increasing the current gradually. I

2. The herein described method of producing bimetallic plates or material which consists in. mounting upon a cylindrical mandrel a sheet-of platinum foil, rotating the platinum foil in an electro-plating bath and raising the plating current from a very low value to a maximum gradually, to produce a heavy adherent deposit, as described.

. FRANK R. McBERTY.

Witnesses:

NICHOLAS E. KERNAN, WILLIAM-G. MCKNIGHT. 

